Machine tool with photoelectric positioning of the work table



'Aug- 20,1945 M. KouLlcovrrcH 2,406,299

.MACHINE TOOL WITH PHO'TOELECTRIC POSITIOYNING LOF THE WORK TABLE Filed Feb. 11,v 1942 2 sheets-sheet 2 Patented Aug. 20, 1946 MACHINE TOOL WITH BHOTOELECTRIC I 'Ifosrriomndor THE WORK TABLE @Maurice "Koulicovitch, Geneva, Switzerland, vas- Asignor to "Societe '.Genevoise ydlnstruments de Switzerland, a firm of 4flihysique, `v(ternera,

:rgSwvitzuer-land lApplication "February 11, m42, Serial No. 430,458

"IiliSwtzveiflalild December-2% @The .object of 1th@ present :invention is Ii a gma- -chineratool 1 with photo electric positioning of :the work table. It will be used with advantage .for .instance .to determine-=the ...position .'of .sliding tables lof. measuring Jnachines rand of precision l.;

tool machines such as center punching machines and precision.drillinglmacliies The usual method for determining a position consists in observing with a microscope the divisions of a scale carried by the movable object and to bring the image of a given division to correspond with a reticle provided in the microscope. This method has the drawback that the precision of the reading depends on the skill of the operator and that the latter has to look intently into the ocular, which operation is fatiguing.

The apparatus according to the present invention is characterized by a photo-electric cell faclng the scale, by a grid inserted between said cell and said scale, and by a source of light arranged in such a way as to send its beams onto the scale. The grid presents spaces open to light (openings or transparent zones) The beams of light coming` from the scale and passing through the grid impress the photo-electric cell, except when the divisions yof the scale cover the open spaces of the grid and intercept the light feeding the cell. In this latter case, there is a corresponding reaction of the cell.

The current variations of the photo-electric cell, amplified if necessary and transmitted further, can control the operations involved in the applications of the apparatus.

In this way, the necessity to look into an ocular and the fatigue resulting therefrom are avoided.

The attached drawings show, by way of example, four embodiments of the object of the present invention.

Each one of the Figures 1 to 4 shows schematically, and with sectional views, one of these embodiments.

In the embodiment shown in Fig. l, the grid I represented partly in sectional view is superposed on a graduated scale 2 which is movable and onto which an electric lamp.3 throws its light. The graduation is traced in black on a transparent background. The grid I presents a, few slits 4a, 4b, 4c, 4d, 4e, by which the light passing through the lighted background of scale 2 can excite a photo-electric cell 5 enclosed in a housing 6. The shape of the slits of the grid I is such that for the determined positions of scale 2, in which these slits superpose themselves onto the graduation of the scale, the light passing through the neiging (ci. 25o-41,5)

grid :I is vdiminished, the .resulting reaction of the :cell `5 producing :a :change in -the l currentjof the outer relectrica1 .circuit `'L yThis circuit 1,

:either .directly,ias,shown in.full^lines,f.or by Zmeans .of a .relay-:8, as shown in .dotted lines, 'operates the;signalingzapparatus'fii.` represented in ithe form .of :a measuringwinstrument, and whichr could be replaced by a control apparatus intended for any function, such as for instance to stop the movable object.

Two other embodiments, in which the graduation is traced in black on a reflecting or a transparent scale, are shown in Figs. 2 and 3.

Fig. 2 shows the case of a surface lighting of the scale and Fig. 3 that of a transparence lighting through the scale, with the same graduation. Lighting, in both embodiments is secured by a source of light 3 with its optical condenser I0 sending its light into the field of the apparatus, either by means of a mirror II, or directly. In both cases, an objective I2 projects the image of the graduation 2 on the gridI; 5 is the photoelectric cell. n Elements 1, 8 and 9 are the same as in the previous figure.

It is possible to superpose a graduation traced in dark on a bright background or in bright on a dark background, or the image thereof, onto a grid provided with slits or with full spaces correspondingI to the tracing; in place of slits, one could use full transparent spaces. One will choose in each particular case the most convenient combination, will characterize the superposition of the graduation and of the grid by a decrease or by an increase of the light received by the photo-electric device.

'I'he graduation 2, the position of which is to be determined, can be composed either of equidistant straight lines, as shown in Figs. 1 to 3, or else of groups of lines, or even of figures, repeating themselves at every unit interval of the graduation. This arrangement has the advantage to permit greater variations of the amount of light passing through a grid made in accordance, and at the same time to obtain a high degree of precision, because each element of the tracing can be thinner and its superposition onto the corresponding element of the grid will be better defined.

If the graduation is composed of groups of parallel lines, there is advantage to arrange that the components of a same group of lines be not equidistant, in order that their exact and total superposition into the grid can only obtain 1n a single ,position deiined for each group of lines.

depending also whether one v The embodiment shown in Fig. 4 is based on In this iigure, one sees the ob- Y with more complex tracings of any` shape'which can be used in the same way in cooperation with a grid made in accordance.

The object of the invention having thusbeenu corresponding to theKV 4 y parts interposed between said scale and said cell, the transparent parts of said grid being spaced apart in correspondence with and being t inv less number than said graduations, and means i Y for directing an illuminated image .of several of said graduations through the gridto said cell.

2. In a machine-tool With photo-electric posi- `tioning of the work-table, in combination, a worktable carrying at least one scale having precision graduations .arranged in succession at spaced points inthe direction of movement of said table,

a photo-electric ycelljfacing said graduations, a grid having transparent and opaque parts interposed between said scale and saidcell, the transparent parts of said grid being spaced apart in correspondence withA and being in less number described and illustrated in the accompanying f drawings, need not beexplained further.

What is claimed to be new is:

1. In a machine-tool with photo-electric positioning of the work-table, in combination, a work-table carrying yat least one scale having precision graduations arranged in succession at spaced points in the direction of movement of said -table, a photo-electric cell facing said graduations, a grid having transparent and opaque .thansaid graduations, and an optical device for projecting an illuminated image Vof several of said graduations through said grid to said cell.

3. An arrangement Las claimed in claim 1, wherein' said graduationsare arranged-in groups and the graduations of eachgroup'arenofdi'ssirnilar'form. VA f V4f. An arrangement'A as claimed in claim *1,

wherein said grid is stationary with respect to said'cell. I Y y Y MAURICE.,KOULI*COI/'ITKJLL` 

